Proximal myotonic myopathy is an inherited disorder associated with proximal skeletal muscle weakness and eye problems. As a rule, the first symptoms appear between the ages of 40 and 50. Currently, only symptomatic treatment is possible.
What is Proximal Myotonic Myopathy?
Proximal myotonic myopathy is a genetic muscle disease that usually does not manifest itself until middle age. So far there have been no cases of congenital diseases. The disease has not yet been observed in children either. Only a very rare juvenile form can occur. See whicheverhealth for Binge Eating Disorder Meanings.
In addition to proximal muscle weakness, there are also eye problems that become noticeable through visual impairments. Other names for this disease include myotonic dystrophy type 2 or Ricker’s disease. The course of this disease is milder than that of myotonic dystrophy type 1 (Curschmann-Steinert disease), which is also hereditary.
However, Ricker’s disease occurs less frequently than Curschmann-Steinert’s disease. The prevalence is estimated at 1 to 5 per 100,000 people. In Germany and the USA, the frequency of the diseases is somewhat higher. The reason for this could be the first occurrence of the corresponding mutation in Central Europe. Due to its genetic cause, the disease cannot be treated causally, but only symptomatically.
Causes
A defect in the ZNF9 gene on chromosome 3 is suspected to be the cause of proximal myotonic myopathy. This gene encodes a so-called zinc finger protein, which contains zinc as the central atom. The corresponding protein interacts with the DNA or RNA and thus influences the gene expression of various genes. The encodable part of the gene is not altered, but the CCTG repeat sequence expands.
This means that an additional CCTG sequence is built into the non-codable region of the gene, which in turn influences gene expression for the ZNF9 gene. The corresponding protein is not genetically modified, but it is not present in the optimal concentration. In some cases, anticipation is also observed.
Anticipation denotes earlier onset of the disease in offspring. In addition, the symptoms are then more pronounced in them. This is caused by more built-in CCTG repeats that can expand more and more from generation to generation. The expansion of CCTG repeats or generally of tetranucleotide repeats is genetically determined.
However, anticipation does not always take place because the number of CCTG repeats does not necessarily correlate with the age of onset of the disease. Proximal myotonic myopathy is inherited in an autosomal dominant manner. The disease is passed on directly from one generation to the next.
Symptoms, Ailments & Signs
Proximal myotonic myopathy can present with a variety of symptoms. The degree of severity of the symptoms is very different. One of the most important features is the development of proximal muscle weakness, which is usually also decisive for the diagnosis of the disease.
The muscles of the pelvis and shoulder girdle are often affected. Muscle weakness is often accompanied by severe muscle pain (myalgia). In 75 percent of cases, increased muscle tension (myotonia) occurs, which is only slowly reduced. The facial muscles are also affected much less frequently (about 12 percent).
A tremor is observed in a third of cases. The heart is also often affected. Cardiac arrhythmias and disturbances in the transmission of stimuli occur. Cataracts (cataracts) appear in the eyes, which lead to a deterioration in visual acuity. Hyperhidrosis (increased sweating), hyperthermia (increased heat production), reduction in the size of the testicles (testicular atrophy) or even diabetes can also develop.
Central nervous disorders, hypogammaglobulinemia (lack of gamma globulins) or bile outflow disorders are sometimes also observed. One complication is malignant hyperthermia. This can be triggered during anesthesia by inhalation anesthetics, depolarizing muscle relaxants or even stress.
Symptoms of this complication are tachycardia, difficulty breathing, cyanosis, muscle rigidity, acidosis, or hyperkalemia. Finally, there is a sharp increase in temperature, which can lead to protein denaturation and circulatory failure.
Diagnosis & course of disease
To diagnose proximal myotonic myopathy, electrical muscle activity is measured in the EMG (electromyogram). If there are monotonous salvos reminiscent of the sound of a dive bomber, a muscle disease is present. For more precise differentiation, a direct gene test is carried out in the leukocytes.
Other examination methods are the clenching test and the percussion test. In the clenching test, a delayed opening of the hand after a clenched fist indicates myotonia. The same applies if muscle contractions lasting a few seconds occur when the affected muscles are tapped (percussion).
Complications
Patients with this disease usually suffer from muscle weakness. In most cases, the symptoms only appear at an advanced age, so that direct prevention or early treatment of this disease is not possible. Unfortunately, no causal treatment is possible either, so that only the symptoms of this disease can be limited.
The patients suffer from severe muscle weakness. This leads to severe pain in the muscles, which occurs primarily under stress. Muscle atrophy also occurs with this disease, which leads to a significantly reduced quality of life. The muscles in the face are particularly affected, so that the patient can no longer move them and thus no longer control their facial expression. Those affected also suffer from tremors and heart problems with this disease.
In the worst case, cardiac arrest can occur. Discomfort in the eyes and a significantly reduced visual acuity also occur and make everyday life more difficult for those affected. There are no complications from the treatment itself. However, this can only partially limit the symptoms. Complete healing is usually not possible. The life expectancy of the person affected may also be reduced as a result of the disease.
When should you go to the doctor?
People who are adults and have severe muscle problems should see a doctor for a check-up. If the symptoms arose as a result of physical exertion, a sufficient period of rest and a restful night’s sleep are usually sufficient. This is followed by an alleviation of the symptoms or a spontaneous healing. A visit to the doctor is not indicated in these cases.
However, if the symptoms persist for several days or if they increase in intensity, a doctor is needed. A decrease in physical performance, limitations in mobility and twitching of the muscle fibers must be examined and treated. Persistent stress, inner restlessness, a general feeling of illness and cardiac arrhythmias should be presented to a doctor.
If sleep disorders appear, if everyday requirements cannot be met or if well-being decreases, there is a need for action. If there are impairments of vision, a decrease in visual acuity and an increased risk of accidents and injuries, the observations should be discussed with a doctor.
A reduction in the size of the testicles, an increase in sweating or an unusual feeling of heat inside the body are causes for concern. General functional disorders, complaints in the pelvic or shoulder area and irregularities in the facial muscles must be presented to a doctor. If muscle pain, repeated tension or discomfort occurs, a doctor is needed.
Treatment & Therapy
A causal therapy of proximal myotonic myopathy is not yet possible. So far, only symptomatic treatments can take place. Mainly physiotherapeutic measures are carried out, which can maintain the ability to walk up to the age of 60. Multidisciplinary care and monitoring is also important.
Monitoring of the heart in particular plays a major role here, because cardiac involvement is often decisive for the prognosis of the disease. If malignant hyperthermia develops, life-saving measures such as mechanical ventilation, administration of dantrolene (a muscle relaxant), cooling of the body and treatment of acidosis should be instituted under intensive care supervision.
Prevention
There are currently no preventive measures to prevent the onset of proximal myotonic myopathy in the presence of a genetic predisposition. The disease is inherited in an autosomal dominant manner. If a parent has the disease, there is a 50 percent chance that the offspring will also be affected. It therefore makes sense to seek human genetic counseling if there is a family history.
Aftercare
In the case of proximal myotonic myopathy, only symptomatic follow-up can currently be carried out. This mainly serves to reduce the painful side effects of the disease. Physiotherapy sessions are suitable for this.
These counteract progressive muscle atrophy and muscle weakness and help to maintain the ability to walk for as long as possible. Regular training sessions and special exercises serve to stabilize the body. Diet plays an important part. A healthy diet provides the body with all the important nutrients.
Furthermore, psychological support helps patients to maintain their inner peace and a more positive attitude despite the illness. Self-help groups can also help people to cope with the illness with the help of other people affected. At home, occupational therapy can make everyday life easier for patients with the use of various aids such as shower chairs, booster seats or grippers.
After the disease with proximal myotonic myopathy, regular follow-up examinations by the doctor are important in order to monitor the heart and muscle wasting and to detect reduced vision in good time. Unfortunately, the prognosis for proximal myotonic myopathy is rather negative.
Since it is a genetic disease, a complete cure is currently impossible. The quality of life is reduced primarily due to progressive muscle atrophy. This decline can also lead to a shorter life expectancy.
You can do that yourself
Proximal myotonic myopathy is a genetic condition. The sufferer has no means to heal himself from this disease. The organism can be positively supported by lifestyle and various techniques, but freedom from symptoms does not occur.
The muscles should be the focus of targeted training. Although the disease causes severe impairments, it is advisable to stabilize the muscular system daily in individual exercises to the best of your ability. The training sessions should be tailored to the needs and limits of the body. The development of a sense of achievement is important because it promotes motivation.
A fundamentally positive attitude towards life is very helpful in overcoming the symptoms in everyday life. The focus of attention should be pleasant experiences and the promotion of well-being. The use of relaxation techniques can be used to increase mental strength. Through meditation, autogenic training or yoga, existing stressors are reduced and at the same time the inner life of the patient is strengthened. This should help to improve the handling of the disease in everyday life. Avoid social withdrawal. Joint activities are perceived by the patients as pleasant and constructive. The exchange in self-help groups brings mutual strength and support.
